Apparatus for removal of electrostatic charges from the surfaces of materials of lowconductivity by means of a stabilized electrical glow-discharge



2,951,968 CHARGES FROM THE Y MEANS Sept. 6, 1960 R. LEUPl APPARATUS FORREMOVAL OF ELECTROSTATIC SURFACES OF MATERIALS 0F LOW CONDUCTIVITY E OFA STABILIZED ELECTRICAL GLOW-DISCHARGE Filed March 25, 1955 4Sheets-Sheet 1 m m L E V u M t w M b I .3 W a, R 2 m a... F 4 4 l n #45/ 5 F \3 J 3 2 Q\v\\\\\\ 2,951,968 FROM THE SURFACES OF MATERIALS 0FLOW CONDUCTIVITY BY MEANS Sept. 6', 1960 R. LEUPl APPARATUS FOR REMOVALOF ELECTROSTATIC CHARGES OF A STABILIZED ELECTRICAL GLOW-DISCHARGE FiledMarch 25, 1955- 4 Sheets-Sheet 2 FIG,6

IN VE N TOR ROBERT LEUP/ 5v V V Richards d 6616/ Attorneys -APPARATUSFOR REMOVAL Di ELECTROSTATIC CHARGES FROM THE Sept. 6, 1960 R LEU2,951,968

SURFACES OF MATERIALS OF LOW CONDUCTIVITY BY MEANS OF A STABILIZEDELECTRICAL GLOW-DISCHARGE Filed Mafch 25, 1955 4 Sheets-Sheet s I Fig.8

Fig.9 I 18 INVENTOR ROBE T LEUP/ mu/A3 05 4 GE/LQ ATTORNEYS Sept. 6,1960 R. LEUPl 2,951,968

APPARATUS FOR REMOVAL OF ELECTROSTATIC CHARGES FROM THE SURFACES OFMATERIALS 0F LQW CONDUCTIVITY BY MEANS OF A STABILIZED ELECTRICALGLOWDISCHARGE Filed March 25, 1955 4 Sheets-Sheet 4 \INVENTOR:

ROBERT LEUPI'" B91 R/cH/MDS f 6.5/51? ATTORNE Y5 United States atentAPPARATUS FOR REMOVAL OF ELECTROSTATIC CHARGES FROM THE SURFACES F MATE--RIALS:OF LOW .CONDUCTIVITY 'BY MEANS OF A STABILIZED ELECTRICALGLOW-DISCHARGE kobertiLeupL'zsarnen, Switzerlandassignorto G. A.

Messen-Jaschin, SarnenySwitzerland .Fil8d'M2l'.'2 5,1955,. Ser. No.496,853

tfil'aimsipriority, .applicationSwitzerland Mar. 26,: 1954 '4 Claims.(Cl.3I5-57) 5.flf his,inve,ntionrelates toa device of the kindserving toremove electrostatic charges from the surface ofill-conduqtipgwmaterials. It is especiallysuited ,to discharge.,materials;.that.arepassing it in the form of ribbons and endless websbut it also permits to remove electrostatic r charges-from the-surfaces.of solid immovable or hardly icharged-amayrdeeply penetrate the space ofdischarge be- :tween: the; electrodes.

. Tfhejrnethodgperlse, is alreadywell .known andsuffiacientlyzproved.

Up=to':;nowh0wever, no"practioal design-of theelecut-rodesshasrbeenyfound that would have satisfiedinrpracnticexwitharespect to operation :and moreover ensured aimiflicientrrapiddischarge of the charged objects.

:Hitherto designs ofelectrodes have been proposed .and .;realized wherethe glowing electrode was equippedby rsharpipoints.andsurrounded by atube of insulating material leaving :thepoints "free in correspondingopenings. Thexinsulatingrt-ubehas the purpose of a PI'OtBCtiVCIdCViCG:against' accidental contact with the high tension :electrode rand:thezfine :points.

:Substantiallymore eifectivethan these electrodes with .=points..areielectrodes having glowing .edges or wires, beaoause the :number :ofglowing ions is necessarily..pro- .-portionedato:the.area.of the glowingsurface. In-this kind rioiielectrodesrthesinsulating tube serves toreceive at least aonetglowing'wire or. at least one metal foil that whenconynecteduto a high-tension source glows at the outwardly r directededge.

I-n-order to make the discharge of a ribbon running over these glowingportions most effective this ribbon should move along said tube or rodin a very little distance or even slide-over it. T his isdisadvantageous in the case where the tension of the ribbon cannotbe:kept sufficiently constantyto ensure a constant distance from thetube. Since due to friction of the ribbon on the tube ofinsulatiingmaterialanew charge will be generated on the ribbon.

It is'anobject of thepresent invention to avoid this disadvantage to agreat extent partly by a greater discharging e'ifeot, generated by theapproaching of acounter electrode-andpartly in that it is made possiblefor the field -to-penetnate deeply in the space of discharge of thestabilizing glow-discharge. This opens the possibility ofasubstantialsimplification and economization of the design.

A 'furtherobject of the invention is to providea cylinfidrical bodyforming one-of the electrodes and serving .at the-same time as supportfor at least one metal wire in- -sul-ated-from 'the support and formingthe second elec- -trddefthat extends parallel to the axis of thecylinder and'exterior'ly ofthe latter.

It has been found that 'not'only ansasymmetricahposi- ;tion' of theglowing wire but also an asymmetrical-position of its counter electrodeinthe insulating body-may beof great importance.

.In the device according to thepresent invention there- 'fore' thecylindrical bodyisan insulating body enclosinng at least one cylindricalaxially directed metallic body parallel ,to ,the insulating body andcoated byit andfilling out aqsmaller portion of the section of theinsulating body, the metallicbody being outwardly displaced with-respectto" the axisoftheinsulating body in the-direction to the glowingwire insuch a-inanner, that only anarrowzone of the insulating bodyis-traversedby the field generating 'the glow discharge.

By this arrangement two substantial advantages are gained. On the onehand the capacity of-the electrode coated by the insulating body may bekept much lower without suffering any loss of field intensity neartheglowingwire, and on theother hand in the case of highfrequency operationof the device, the high frequency thereof.

'In order to get a correct screening of the highfrequencyfield'emitting-from the inner .or the counter electrode respectively,the cylindrical body for screening thehigh frequency field may besurrounded by at least onenot glowing groundedmetalpart, which leavesthe grounded glow wire generating ions free. Suitably the not glowingmeta'l part-is not arranged nearer tothe glowwire than theglow wire-isdistantfrom the cylinder, so that the field extending from the materialto be discharged is able to penetrate deep-enough in the space ofdischarge between glow wire and counter electrode.

By way of-example specificembodiments of the present invention arerepresented in the accompanying .drawings.

"Figspl to 4 and 1a to 4a are axial-andcross-sections illustrating--four discharging :devices according to the invention.

Figs. "5 6 show variousarrangements of the high .frequency transformerin the device according to Figs. 14. Fig. 7 illustrates the simultaneousapplication of the high "frequency transformer as .a mechanicalsupport.for 'a' cantilever cylindrical electrode.

Figs.'8, 8a are axialand-cross-sections, respectively,

"of a first-example.

*-Figs..9--and 9a are axial-andcross-seotions of:a. second example.

Figs. 10 and 10a are axialand cross-section .of :a modification withrespect to Figs. 2, 2a, respectively.

Figs. 11, 11a show in side View and section,:respective- 'ly,-a. furthermodification of the example according to -Figs.'-9, 9a.

Fig. -12 aside view ofa part of the first embodiment of the device.

. ignates-a;cylindrical metallic'hollow or solid body,-which at both ofits'ends is provided with two metallic supports The latter are insulatedfrom the body by meansof insulatingportions "3. The supports 2 serve forthe .attachmen't of wires 4, which extend parallel with respect tO=th6-3.XiS Of the .cylindrical body :1 and are-covered by a glow-layer assoon as sufiiciently high electrical voltage is present between thesupport'2 and the cylindrical metal body 1 by connecting these partswith a suitable source of voltage. The voltage can be led to the inaxial direction, form a wire-electrode, which may be earthed. Theelectrode 1 carrying the voltage is then screened by an earthedwire-electrode, forming a cage and protecting that electrode from beingcontacted. The

, separate wires of the wire-electrode glow during operation despitebeing earthed, since the glow discharge is only dependent of the fielderected above said wires and not of the absolute potential of the wires.Also in the case of the Saint Elmos fire, the luminous objects areconnected to earth.

The spacing between two adjacent wires 4 should at least be equal totheir distance from the cylindrical electrode 1 in order that the fieldof the body to be discharged will reach sufiiciently into the dischargespace of the glow discharge and thereby will be fed with the ionsnecessary for discharge.

The wire cage-electrode provides an effective protection againsttouching since the field at the wires will be homogenised upon approachof a hand to the extent that it will no more be sufficient to keep upthe glow discharge and no electrifying effects are experienced.

An effective protection of the voltage-carrying electrode can also beachieved with less wires in that according to Fig. 2 the cylindricalmetallic body 1 is provided with an insulating layer 5 of gooddielectric break-down properties or in that according to Fig. 3 thevoltage-carrying electrode is arranged as a conductive layer 6 in a tube7 of insulating material. In order to prevent flash-overs the ends ofthe insulating tube 7 can be provided with stoppers of insulatingmaterial which are glued into the tube to give a certain break-downsafety to the assembly.

Another embodiment of the device is shown in Fig. 4. Here the voltagecarrying electrode is formed by a metallic body 8 such as a metal tube,which is only supported by the tube covering portions 9 at both of itsends or insulators, inserted into this tube. Also in this case the tubecovering portions may be glued in for break-down safety.

In order not to necessitate a high tension cable for feeding the highvoltage, which would be unhandy, suitably high-frequency currents areused, which are transformed in a small Tesla-transformer it) to highvoltage,

which transformer may suitably be attached to one end of the device. Thecoil body of the secondary coil of this Tesla-transformer may at thesame time have the mechanical function of one of the insulation coils 3or 9, respectively, in one of the embodiments according to Figs. 1, 2 or4, as for instance shown in Figs. 5 and 7. When using a tube ofinsulating materials the Teslatransformer it is suitably mounted intothis tube as shown in Figs. 6 and 7. This provides a certain protectionfor this transformer against damage and there will I be less danger ofinadvertently touching said transformer.

In all cases where the wire electrode is connected to earth there willbe no difliculties in insulating the feed ,tallic support 2 of thesuspended wire may be fixed at the height of this winding at the tube asshown in Fig.

7 without charging the secondary winding with an additional capacity. Inthe same manner also the other support 2 may be fixed on the insulatingtube 7 if the tube is extended correspondingly over the voltage carryingelectrode at this point. This manner of attachment of the supports 2 hasthe advantage that the device may suitably be secured at both of itsends by means of brackets or that the tube ends serve at the same timeas handles.

In the embodiment according to Figs. 8 and 8a a cylindrical insulatingbody 12 is provided, which is formed as a round bar. The insulating body12' is provided with an eccentric longitudinal bore, in which a metallicrod 13 forming one of the electrodes is arranged. By means of end plates14 two wires 15 diametrically and parallely extending with respect ofthe axis of the insulating body are suspended. The wire 15 being shownas situated above the other wire in these figures, serves as glowelectrode.

In the embodiment according to Figs. 9, 9a the cylindrical insulatingbody is formed by a tube 16 in which a cylindrical rod-electrode 13 iseccentrically arranged with respect to the tube 16 but parallel to theaxis of the latter by means of the holder 17. Otherwise the constiuctionof the device is the same as in the first described embodiment.

in the modification according to the Figs. 10, 10a of the previouslydescribed embodiment, two cylindrical metallic electrodes 18 arediametrically arranged within 7 the tube 16, forming the insulating bodyand eccentrically with respect to the axis of the latter.

These two metallic electrodes 18 are electrically connected with eachother.

In the modification shown in Figs. 11 and 11a the cylindrical insulatingbody is formed by a two-part tube 19, its two-parts being diametricallyopposed to each other. Also in this case a cylindrical metal electrode18 is eccentrically arranged within this tube. By means of the two-partconfiguration of the tube 19 longitudinal slots 20 are formed, whichpermit a further reduction of the high-frequency loss. Thereby theinsulating body must naturally fill out a sufficiently large spacebetween the metal electrode and the glow-wire, in order to stabilize thedischarge in that space with respect to a spark or arc discharge. t willbe understood that also in this case two metallic electrodes 18,corresponding to the modification according to Figs. 10 and 10a might beprovided.

Similarly the insulating bodies 12 and 16 ofthe embodiments according toFigs. 8 to 10 might be provided with longitudinal slots to reduce thehigh frequency losses. In all described embodiments the cylindricalmetal body 13 and 18, respectively, forming the inner electrode iseccentrically arranged with respect to the axis of the insulating body,and towards the corresponding glow wire 15, such that only a narrow zoneof the cross-section of the insulating body will be situated between themetal electrode and the glow wire, which will be penetrated by thestrong field generating the glow discharges. Further this metalelectrode 13 and 18, respectively, will fill out in all cases only asmall portion of the total cross-section of the insulating body.

In order to minimise the glow-losses of the electrode built into theinsulated body, these electrodes are given a circular or ellipticcross-section and are provided with ball-shaped end portions.

In Figs. 12 to 14, M. designates the cylindrical body, which in theembodiments shown, is formed as a tube.

7 Two holding rings 22 are seated on the tube 21 and are axially spacedfrom each other. Between these holding rings a glow-wire is extendeddistanced from the outer surface of the tube 2.1; and parallel withrespect to the tube axis by means of screws 23.

In the embodiment according to Figs. 12 and 13 a second wire 24 isextended between the holding rings 22 parallel with respect to the tubeaxes and diametrically opposed to the first glow-wire. The tube 21 isconstituted by an insulating body. In the same diameter as the wire ielectrodes 24, one of which is formed as a glow-electrode,

a counter-electrode formed by a cylindrical metal rod 25 is arrangedwithin the tube 21. The metal rod 25 is distanced from the tube axis andextends parallel thereto. At the rings 22 a screening cover 26 issecured, which surrounds a part of the insulating body 21 intrough-shaped configuration without obstructing thereby the upperglowelectrode 2 4. The distance of the cover 2 6 from the insulatingbody 21. must at least be equal to the distance of the glow-electrode 24from the insulating body 21. In the embodiment shown the firstment-ioneddistance is somewhat larger than the second-mentioned distance. Thewires 24 and the cover 26 are connected to earth, while the counterelectrode 25 carries voltage.

In most cases it will be sufiicient to give the remaining spacing 27(Fig. 13) double the width of the distance between the glow-electrode 24and the electrode 25 or the insulating body 21, respectively. Therebythe field emitted by the material to be discharged may penetratesufliciently into the discharge space between the glow electrode 24 andthe electrode 25 or the insulating body 21, respectively and it willthus be possible to collect the ions from this space necessary for thedischarge of the material.

Tests have shown that in many cases a metallic protecting-cover willalready by sufficient, the edge tangent surface of which will justcontact the insulating body 21 if the glow electrode 24 connected toearth will extend in the middle of this spacing 27 as shown. In order toprevent glowing of the protecting cover the latter is crimped at itsends 28 with a sufiiciently large radius.

In the embodiment according to Figs. 14 and 15 a plurality of metallicwires 29, which are suspended in the same manner as the glow wire 24between the holding rings 22 and with the same angular spacing withrespect to each other or the glow wire 24, respectively, serve as ascreen. The metallic wires 29 include a larger radial distance withrespect to the tube axis than the glow wire 24- and further theircross-section is larger than that of the glow Wire. In this case thetube 21 is made of metal and forms the voltage carrying electrode 29.

It will be understood that also when using a counterelectrode 25according to Figs. 12 and 13, eccentrically arranged in the insulatingbody, the screen may be formed by suspended wires 29.

In both embodiments shown, the plane of symmetry extending through thelongitudinal axis of the device and through the glow wire 24 will beperpendicular to the plane of the material to be discharged.

The screen metal portion could also be formed by an other suitableapparatusor machine-pant.

I claim:

1. An apparatus for the removal of electrostatic charges from thesurfaces of materials of low conductivity by means of a stabilizedelectrical glow-discharge comprising a metallic cylindrical body formingan elongated electrode, an insulating member at each end of said body,supporting means carried by each insulating member, and a metallic wireforming a second electrode extended between said supporting means atboth ends of said cylindrical body in parallel relation to the axisthereof exteriorly of said cylindrical body forming the firstmentionedelectrode, wherein a hi h-voltage transformer is mounted between one endof the cylindrical electrode and the adjacent supporting means, in orderto generate the voltage required for operating the glow-electrode.

2. An apparatus as claimed in claim 1, in which the secondary of saidhigh voltage transformer is wound on a coil body serving as support forsaid cylindrical metal body.

3. An apparatus for the removal of electrostatic charges from thesurface of materials of low conductivity by means of a stabilizedelectrical glow-discharge comprising a metallic cylindrical body formingan elongated electrode, an insulating member at each end of said body,supporting means carried by each insulating member, and a metallic wireforming a second electrode extended between said supporting means atboth ends of said cylindrical body in parallel relation to the axisthereof exteriorly of said cylindrical body forming the first-mentionedelectrode, wherein a high voltage transformer generating the voltagerequired for operating the glow-electrode is built into one end portionof said cylindrical body formed of insulating material.

4. An apparatus as claimed in claim 3, in which the end of said hollowcylindrical body remote of said transformer is provided with a glued-instopper for preventing electrical break-down.

References Cited in the file of this patent UNITED STATES PATENTS414,356 Wirt Nov. 5, 1889 565,777 Moore Aug. 11, 1896 1,249,429 LewisDec. 11, 1917 1,260,750 Bryant Mar. 26, 1918 1,985,058 Rath Dec. 18,1934 2,071,464 Henderson Feb. 23, 1937 2,228,276 Le Van Jan. 14, 19412,505,993 Rogers May 2, 1950 2,624,858 Greenlee Jan. 6, 1953 2,629,839Greenlee Feb. 24, 1953 2,651,004 Acton Sept. 1, 1953 2,660,685 JohnsonNov. 24, 1953

